V for Very efficient

By Anna Tiley

Why birds fly in a V formation has interested scientists for a long time and has led to a number of theories to explain the behaviour. New research published last week in Nature has provided a possible answer.

Previous theories for the V formation include that it enables the best navigators to be at the front of the flock and that the shape reduces the risk of attack by predators.

However, it is more likely that flying in a V-shape is actually a way of minimising energy expenditure during flight.

Flamingos

In 2001, a study on pelicans found that the heart rate of the bird at the tip of the V was higher than its companions behind, suggesting differences in the amount of energy the birds were putting into flying.

Research published last week from a different group added to this data and gave further interesting results.

Scientists from the UK and Austria investigated flying behaviour in the northern bald ibis. They attached data loggers to each bird and tracked its position, speed and movement within the flock during flight.

The results showed that the birds position themselves within the V-shape in the most aerodynamically optimal positions and synchronise their wing beats.

When a bird beats its wings, it creates two types of air flow known as downwash and upwash. Downwash is a downward air flow which isn’t beneficial to birds behind as it pushes them downwards.  Upwash on the other hand is upward moving air which can help the bird behind create lift without using as much energy.

By carefully positioning itself within the flock, a bird is able to benefit from the upwash created by individuals at the front. Synchronising wing beat and optimising position within the flock can also help reduce energy expenditure.

The results from this research are interesting and may also have further advantages. For example, understanding how birds take advantage of the air streams created by each other’s wing beats could be used to improve efficiency in flight planning.

 

Exciting video by researchers explaining it all:

http://www.youtube.com/watch?v=fKkzqk3RMLc

 

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